Scientific studies show that: the release of harmful substances such as formaldehyde, benzene and the like in home decorative materials continues 10˜15 years, or even longer, which seriously affects the life and health of occupants. Therefore, increasingly demands are put forward in environmental performance of the decorative materials. The environmental performance of wall paint especially draws the attention of the public because the wall paint acts as the main material of interior decoration. Currently, the conventional environment-friendly wall paints mainly include water-based paint, latex paint, multicolor paint, enamel paint and so on. These types of wall paints can not absorb and eliminate formaldehyde, benzene and other harmful substances released by other decorative materials although they are substantially free of the formaldehyde, benzene and other harmful organic substances.
Some air-purification wall paints that can absorb and eliminate harmful compounds in the air have been gradually invented with the study of the wall paint. As disclosed in CN Patent Application No. 201010578500.5, for example, a bamboo charcoal wall paint containing bamboo charcoal factor and anion additive is disclosed, the bamboo charcoal factor is able to adsorb and decompose formaldehyde, ammonia, benzene and other harmful gases in the air, and the anion additive is able to release anions. However, as we all known, the bamboo charcoal factor has a certain adsorption capacity, which would not adsorb harmful substances in the air once the adsorption capacity becomes saturated, and thereby lose its effectiveness. In addition, the harmful substances adsorbed in the bamboo charcoal factor will inevitably cause secondary pollution as can not be decomposed or degraded timely and then deposited in the wall paint.
Research found that anatase nano-titanium dioxide can produce hydroxyl radicals (OH—) and negative oxygen ions (O2−) after absorbing light energy, which has strong redox ability and can decompose and oxidize pollutants in the air, so as to achieve the purpose of air-purification. The nano-titanium dioxide under 10 nanometers has particularly excellent photocatalytic properties. Thus, the wall paint manufacturers are trying to add anatase nano-titanium dioxide into the wall paint, as disclosed in CN Patent Application No. 201010624630.8. However, the nano-titanium dioxide sol easily flocculates to enlarge particle size and then precipitates once it is added into a coating system during practical production, and the photocatalytic property of the nano-titanium dioxide coating is greatly reduced or even lost after flocculation. The prior art has not solve the problems of compatibility of the anatase nano-titanium dioxide sol under 10 nanometers and the coating system, and dispersion of nano-titanium dioxide particles in the coating system.